1. Field of the Invention
The present invention relates a PC (Personal Computer) card to be mounted in a computer system and, more particularly, to a PC card that is detachably mountable in a 16-bit card slot or a 32-bit card slot.
2. Description of the Related Art
A PC card is a peripheral device that has been developed to help extend the functions of a personal computer. Standards of the mechanical and electrical characteristics of PCs are now being formulated under the aegis of PCMCIA (Personal Computer Memory Card Interface Association) and JEIDA (Japan Electronic Industry Development Association). Besides memory cards, a plurality of different PC cards including flash memory cards, HDD (Hard Disk Drive) cards, and FAX/MODEM cards are now commercially available.
These cards are classified into 8-bit cards, 16-bit cards, 32-bit cards and the like according to the particular internal data bus width. The PC card slots of personal computers which are commercially available may receive any type of PC cards. However, some conventional personal computers can only receive 16-bit cards and 32-bit cards cannot be inserted into their PC card slots.
According to the standard, a projection is provided in the card slot of a personal computer to identify the type of a PC card being inserted. A groove which is deep enough to receive the projection is provided in the vicinity of a connector of the PC card. The standard specifies that the height of the projection for a 16-bit PC card slot be higher than that of a 32-bit PC card slot. The projection serves as an obstacle, making it impossible to insert a 32-bit card having a shallower groove into a 16-bit PC card slot. Since the driving voltage of the 32-bit card is 3.3 V while the driving voltage of the 16-bit card is 5.0 V, such a setting advantageously protects the internal circuitry of the card.
The standard also specifies that the top surface of the connector of the 32-bit PC card be provided with a predetermined number of projecting portions producing a ground terminal having a predetermined height. The projecting portions are intended to assure the connection between a circuit board in the PC card and the ground of the personal computer, and to perform reliable and fast data transfer between the PC card and the computer. Such a requirement is not imposed for the 16-bit PC card.
As the performance requirements of the personal computer increase, the bus of the PC card generally shifts from an 8-bit width to a 16-bit width and to a 32-bit width. Most new PC cards currently on sale are of the 32-bit variety. However, there are many users who still use personal computers having only 16-bit card slots. A new PC card capable of operating in both 32-bit mode and 16-bit mode may be accepted by many more users.
The standard, however, does not permit the 32-bit card to be inserted into the 16-bit card slot. Even if the groove is deepened, the projecting portions on the connector still restrict the insertion of the card into the slot.